Master Cylinder Flange

Dave Lenzi called my attention to the following problem; he has checked all current production units from all suppliers all of which are made in China and all of which have the same problem. The master cylinder on the right is a new Raybestos OEM Master Cylinder. As you can see the flange had to be ground down from 0.670 to 0.500 inches. If you don't do this when you install it and the bracket the nuts that hold it on to the booster will only have three threads engaged. The booster can apply over 1000 psi pressure to the master cylinder. Obviouolsy having three threads engaged is NOT good! Use 3/8 x 18 self locking flange nuts after modifying the master cylinder.